Voltage regulation



Nov. 19, 1957 M. H. HAYES 2,814,014

VOLTAGE REGULATION Filed April 2, 1954 impedance variations. It is alsodesirable that United States P a o.

This invention relates to voltage regulating apparatus and morespecifically to an improved means for supplying direct current from asource of very low. impedance at a constant potential.

In the electrical arts generally, and particularly'inrthe computer,automatic control, instrumentation andcommunication arts, many wellknown and widely used circuits require constant potential direct currentpower.- In

order to achieve accurate computation, reliable control, accurateinstrumentation or undistorted communication, it is usually necessarythat ample direct current power supplied to such circuits be maintainedat a constant potential regardless of supply voltage fluctuations orload suchpower be supplied with a minimum of waste.

Various means for effecting regulation-are well-known. Thermionicemission devices placed in series with a load usually offer rapidresponse to voltage fluctuations, but such devices are capable ofsupplying only small amounts of current. Gaseous discharge devices suchas thyratrons are usually capable of supplying greater current, but havea disadvantageous time delay in response. 1 Since thyratron controlseflect changes in output voltage level by varying the time of conductionof the thyratron-during each cycle, voltage fluctuations which occur atfrequencies higher than that of the input supply to the thyratron arenot smoothed .out by a thyratron control.

.. Shunt regulating tubes provide an extremely rapid correction of highspeed voltage fluctuations, and because load current need not flowthrough such tubes, ample reg ulation may be provided for high currentpowersupplies using such tubes. However, due to the limited currentcapacity of a shunt connected regulating tube, it is necessary that suchtubes be maintained at optimum operating potentials in order to correctrapid voltage fluctuations. For example, if a shunt regulating tube isconducting near saturation in order to correct a gradual or maintaineddecrease in load impedance, a rapid variation in load impedance or inputpotential may not be adequately and quickly corrected by the shunt tube.The present invention overcomes the above mentioned disadvantages ofprior art devices by providing in combination a thermionic-emissionshunt regulator capable of extremely rapid v response to voltagefluctuations, and a magnetically-controlled source regulating meansoperable to maintain the shunt regulator at its optimum operating point,so that wide excursions in load impedance or supply voltage do notaffect control response.

It is therefore a primary object of the invention to provide an improveddirect current power supply which will present an extremely low sourceimpedance to a load.

It is another object of the invention to provide an improved directcurrent power supply capable of supplying an improved full-wave'rectified direct current power large amounts of current at a constantpotential, regard- .load may be connected thereto.

supply deriving its power from any alternating current sourceand'delivering a constant potential direct current output'irrespective offluctuations in the alternating current source potential or variationsin the direct current output. load. 1 O'ther'objects of the inventionwill in part be obvious and will in part appear hereinafter. It Theinvention accordingly comprises the features of construction,combinations of elements, and arrangements of parts which will beexemplified in the constructionhereinafter set forth, and the scope ofthe invention will be indicated in the claims. For 'a"fullerunderstanding of the nature and objects of theinventicin reference maybe had to the following detaileddescription taken in connection with theaccompanying drawing, in which certain well-known elements are shown inblock diagram form for the sake of clarity, and wherein correspondingparts are identified by like referencev characters:

Fig-.1 is. an"el'ectrical schematic diagram of one preferred-embodimentof my invention; 1;; :Fig. :2'is an electrical schematic diagram of analternative embodiment of my invention, and :i-Fig'. 3 illustrates oneform of internal reference voltage source which may be employed forfurnishing amplifier anodevoltages in practice of my invention.

Referring now in greater detail to Fig. 1 there is shown a pair of inputterminals L to which an alternating supply voltage may be connected. Thevoltage from the supply isapplied through reactance windings 1 and 2 ofsaturable reactor M to terminals 4 and 5 of the primary winding oftransformer 6. The control winding 3 of saturable reactor M is connectedas shown to ground and through resistance 13 to terminal 14. As iswell-known in the electrical arts, the reactance of windings 1 and 2 maybe varied by variation in current supplied to control coil 3.

Hence it will be apparent that by variation in voltage applied; toterminal 14, the voltage applied to the primary winding of transformer 6may be varied. The secondary terminals 7 and 8 of transformer 6 areconnected in conventional manner to a full-wave rectifying circuitcomprising selenium rectifiers 11 and 12. Vacuum diodes or gaseousrectifiers may be substituted for selenium rectifiers 11 and 12. Thepositive output terminal 15 of the rectifying circuit is connected toconductor 35. The negative output terminal 9 of the rectifying circuitis connected through a conventional filter choke 10 to ground.

Hence the direct current output voltage of the power supply appearsbetween conductor 35 and ground, and the Capacitor 16 may be connectedbetween conductor 35 and ground to aid in smoothing out voltagevariations.

Conductor 35 is also connected through resistor 17, potentiometer 18 andresistor 19 to the negative terminal of a direct current voltagereference source A, which may comprise a battery or any other source ofconstant voltage. The positive terminal of reference voltage source A-isconnected to ground. In operation of the invention, potentiometer 18 isadjusted so that its wiper arm 20 lies very nearly at ground potential.The voltage on the wiper arm 20 is connected as shown to the controlgrid of a direct-coupled amplifier triode 21, the cathode of whichisconnected to ground. Since the potential of reference source A remainsconstant, voltage excursions of supply conductor 35 will produce anerror signal bedecrease in voltage on conductor 23 and an increase involtage on conductor 24. The rise in voltage on conductor 24 will causea rise in voltage at the wiper arm 40 of potentiometer 37 and at thecontrol grid of a cathodefollower triode 25. The increased currentthrough oath ode follower 25 will cause an increased voltageon-conductor 27 and the grids of shunt regulator tubes 28, 29, 30. Thevalue of cathode resistor 26 is chosen so that the shunt regulatorthermionic emission tubes 28, 29,30 are normally-biased in the middleregion of their characteristic curve. A rise in voltage on conductor 27makes the shunt regulator tubes 28, 29, 30 conduct more plate current,and the increased current drain causes a lower voltage to appear onconductor 35 due to the increased voltage drop through the impedances'of rectifiers 11 and 12, transformer 6 and saturable reactor M. Sincethe amplified error signal applied to the grids of the regulator tubes28, 29, 30 is direct-coupled from wiper arm 20, the corrective action ofthe regulator tubes will be instantaneous, regardless of the frequencyof the voltage excursion on conductor 35.

If the voltage excursion on conductor 35 is of great magnitude, theshunt regulator tubes 28, 29, 30 would be cut 011 or saturated, andhence made ineffective to control rapid voltage fluctuations onconductor 35, were it not for the novel source regulating means providedin the invention to maintain the shunt regulator tubes at their optimumoperating point. The rise of voltage on the arm 40 of potentiometer 37causes greater current to flow through triode 41, decreasing the voltageon conductor 42 and hence decreasing the current supplied to the controlcoil 3 of saturable reactor M through terminal 14 and resistor 13. Sincethe control coil 3 has appreciable inductance, current changes in thecoil will occur more slowly, and hence the corrective action caused bythe saturable reactor will occur only if the voltage excursion onconductor 35 persists for an appreciable period of time.

It is to be understood that any desired number of shunt connectedthermionic emission devices, such as thermionic valves 28, 29, etc., maybe employed. Shunt regulator valves 28, 29, etc. are preferably lowimpedance high current thermionic tubes such as Type 6AS7. I

Reference voltage source C, which applies anode potential to triode 41,may comprise a battery or any other source of constant voltage, as forexample a selenium rectifier source as shown in Fig. 3. p I

Reference is now had to Fig. 2 of the drawing which discloses analternative form of magnetic input control which may be employed in lieuof the saturable reactor M of Fig. 1. In Fig. 2 the line L is connectedto a motor 45 which drives a dynamoelectric generator 46 through acommon shaft 47. In the circuit of Fig. 2, the generator 46 isrepresented as an alternator, having its output connected to the primaryterminals 4 and 5 of highvoltage transformer 6. The secondary terminals7 and 8 are connected through rectifiers 11 and 12 to terminal '15, andthe center tap 9 is connected through choke to ground in the same manneras shown in Fig. 1. Alternator 46 has a field coil 48 which is connectedto the cute put terminals of an amplidyne generator 49. An excitationcoil 519 is connected through a variable resistor 51 to a source of D.C. potential 52, here'represented as a battery although it will beunderstood that any other D, C. excitation source may be employed, asforexa'mple the source illustrated in Fig. 3. A second excitation coil53 is connected between ground and resistor13, thev other side of whichconnects to terminal 14, conductor42 and the anode of tube 41 in Fig. l.U I

When terminals 14 and 15 in the circuitof -Fig. 2 are connected to thecorresponding terminals of Fig. 1, in lieu of the saturable reactorinput means M, a risein voltage at the anode of tube 41 which may resultfrom an incremental decrease in potential on conductor 35fa's describedabove in reference to Fig. 1, will cause increased current to flowthrough excitation coil 53 of amplidyne generator 49, thus increasingthe excitation current through field coil 48 of alternator 46 andresulting in a corresponding increase in voltage applied to the primaryterminals 4 and 5 of transformer 6. A corresponding incremental increasein D. C. output voltage occurs to maintain the output constant.Conversely, any decrease in voltage at the anode of tube 41, which maybe caused by an incremental increase in voltage on conductor asdescribed above, will result in a decrease of excitation current throughcoil 53, with a corresponding decrease in voltage applied to the primaryterminals 4 and 5 of transformer 6, thus maintaining the D. C. outputvoltage on conductor 35 constant.

Variable resistor 51, in series with excitation coil 50 and excitationsource 52 of Fig. 2, provides a convenient means for manually adjustingthe excitation current through field coil 48 of alternator 46, and hencefor adiusting the potential applied to primary terminals 4 and 5 of highvoltage transformer 6.

It is to be understood that while I have shown an amplidyne generator 49as connecting means between excitation coil 53 and alternator field coil48, the amplidyne 49 may be omitted entirely, if desired, and theconnection from resistor 13 to coil 53 may be transferred directly toexcitation coil 48. If this is done, then the other end of field coil 48should be connected to ground, so that variations of anode potential ontube 41 and conductor 42 will be directly refiected in the excitation ofgenerator 46.

One of the advantages afiorded by the input circuit of Fig. 2 is thatthe power supply of the invention may be operated from either an A. C.or D. C. line source L, depending upon whether the motor 45 ofmotor-generator set 45 -46 is an A. C. motor or a D. C. motor. Byemploying a universal A. 0-D. C. motor to drive generator 46, the powersupply may be operated from either A. C. or D. C. line sources withoutrequiring any change in the driving motor 45.

It will also be apparent to those skilled in the art that by employing aD. C. generator in lieu of the alternator shown at 46 in Fig. 2, thetransformer 6, choke 10, and rectifiers 11 and 12 may be eliminated andthe output of the D. C. generator may be connected directly betweenterminal 15 and ground. If this is done, terminal 14 should be connectedto the field or excitation coil of the D. C. generator. In such acircuit, the combined input and output voltage regulating means stillfunctions as described above to maintain a constant D. C. potential onoutput conductor 35. However, as the invention may find its greatestutility in high voltage power supplies, and because of the difiicultyand expense of building satisfactory high voltage D. C. generators, itis considered that the use of an alternator 46 with a high voltagestep-up transformer 6 and associated rectifiers 11 and 12 is preferablein particular embodiment.

While I have shown thermionic emission devices as the elements 21, 22,25, 28, 29 and 41 in my preferred embodiment, it is to be understoodthat other amplifying means, as for example cold cathode vacuum tubes orsemiconductor devices, may be employed for these elements withoutdeparting from the scope of my invention.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are 'efiici'ently attained and,since certain changes may be made in the above construction anddiflerent embodiments of the invention could be made without departingfrom the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawing shall beinterpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. Voltage regulating apparatus for supplying constant potential to aload comprising a source of voltage connected to supply a load, athermionic emission device connected in shunt circuit relationship withsaid load, said thermionic emission device having an anode and cathodeconnected to opposite terminals of said load and a control electrode,and being normally biased to conduct substan tially in the middle regionof its characteristic, means for comparing the voltage across said loadwith a reference voltage to produce an error voltage, means foramplifying said error voltage, means applying the amplified errorvoltage to said control electrode, and magnetically-controlled sourceregulating means connected to vary said source voltage so as to maintainthe average potential on said control electrode substantially constant.

2. Apparatus as in claim 1 in which said magneticallycontrolled sourceregulating means comprises a saturable reactor having reactance coilsconnected to vary said source voltage and a control coil responsive tothe amplified error voltage to vary the reactance of said reactancewindings.

3. Apparatus as in claim 1 in which said magneticallycontrolled sourceregulating means comprises a dynamoelectric generator having excitationmeans responsive to the amplified error voltage to vary the outputpotential of said generator.

4. Voltage regulating apparatus comprising a source of voltage connectedto supply a load, a thermionic emission device connected in parallelwith said load, said thermionic emission device having an anode andcathode connected to opposite terminals of said load and a controlelectrode, means biasing said thermionic device substantially in themiddle portion of its characteristic, means for deriving a firstpotential proportional to the deviation of the voltage across said loadfrom a desired value, direct coupled amplifying means for amplifyingsaid first potential and for applying the amplified potential to saidcontrol electrode, and variable impedance means responsive to said firstpotential for varying said source voltage so as to maintain the averagecurrent through said thermionic emission device substantially constant.

5. Voltage regulating apparatus of low source impedance for supplyingconstant potential to a load comprising a source of voltage connected tosupply a load, a thermionic emission device connected in parallelcircuit relationship to said load, said thermionic emission devicehaving a cathode connected to a first terminal of said load, an anodeconnected through a resistance to an opposite terminal of said load, anda control electrode; said thermionic emission device being biased tosubstantially the middle region of its characteristic, a voltagereference source, means for comparing the voltage across said load withsaid voltage reference to obtain an error voltage, direct-coupledamplifying means to amplify said error voltage and to apply saidamplified error voltage to said control electrode, and variableimpedance control means of substantial time-constant responsive to saiderror voltage for varying said "source voltage whereby the averagecurrent through said thermionic emission device is main tainedsubstantially constant.

6. A constant potential direct current power supply comprising amagnetic inductor having motor drive means adapted for connection to aline source of electrical power, means coupling said magnetic inductorwith potential responsive amplifying means, excitation means on saidmagnetic inductor for influencing the potential output thereof, meanscoupling the output of said amplifying means with said excitation meansto effect opposite changes in instantaneous excitation corresponding toincremental variations in potential, and potential responsive variableload impedance means coupled with the output of said inductor to varythe current drain thereon di rectly with instantaneous incrementalchanges in the potential output thereof.

7. A constant potential direct current power supply comprising asaturable magnetic reactor having a pair of reactance coils and aseparate control coil, means for connecting one end of each of saidreactance coils to a source of alternating current, an electricaltransformer, means connecting the opposite end of each reactance coil tothe primary winding of said electrical transformer, electrical currentrectifying means connected with the secondary of said transformer,potential responsive amplifying means connected with the rectifiedoutput potential from said rectifying means to magnify any incrementalchanges in the potential thereof, means coupling the output of saidamplifying means to said reactor control coil to effect instantaneouslyan opposite change in said reactor output potential for each incrementalchange in said rectified output potential, and further potentialresponsive variable impedance means connected in shunt relation withsaid amplifying means and with said rectifying means to vary a shuntimpedance across said rectified potential output inversely with saidincremental changes in the potential thereof.

8. A constant potential direct current power supply comprising incombination an inductive alternator having motor drive means adapted forconnection to a line source of electrical power, variable excitationmeans coupled with said alternator, electrical transformer meanscoupling the output of said alternator with electrical rectifying meansto convert the current output from said alternator to a direct currentpotential, means connecting said rectified direct current potential withamplifying means adapted to magnify any instantaneous incrementalvariations in said direct current potential, means coupling the outputof said amplifying means with said variable excitation means to effectopposite variation of excitation corresponding to incremental variationsin said direct current potential, and further potential responsivevariable impedance means connected in shunt relation with said rectifieddirect current potential and with said amplifying means to effectinstantaneous variation in the current drawn from said rectifying meansin direct proportion to instantaneous incremental variations in saiddirect current potential.

9. Voltage regulating apparatus for supplying constant potential to avariable load comprising, an input circuit adapted to be connected to asource of electrical power, variable impedance source regulating meansconnected to said input circuit, an output circuit adapted to be connected to a load, a thermionic emission device connected in shuntrelationship with said output circuit, said thermionic emission devicehaving an anode and a cathode connected to opposite terminals of saidoutput circuit, a control electrode of said device connected with meansnormally biasing said device to conduct substantially in the middleregion of its characteristic, means for comparing the voltage acrosssaid output circuit with a reference voltage to produce an errorvoltage, means for applying said error voltage to said source regulatingmeans to vary the impedance thereof, and direct coupled amplifying meansfor applying amplified error voltages directly to the control electrodeof said shunt connected thermionic device.

10. Voltage regulating apparatus for supplying constant potential to avariable load comprising, a variable impedance input circuit adapted tobe connected to a power line, a potential responsive impedance controlelement in said input circuit, a low impedance output circuit adapted tobe connected to a variable load, a thermionic emission device connectedin shunt relationship with said output circuit, said thermionic emissiondevice having an anode and cathode connected to opposite terminals ofsaid output circuit, a variable potential bias means, a controlelectrode of said thermionic device connected to said variable potentialbias means, a reference'potential sogrce, means for comparing thevoltage acrosssaid output terminals with said reference potential toprodlice 'an error voltage, means for amplifying said error voltage,means including said variable bias means for applying the amplifiederror voltage to the control electrode of said thermionic device to varythe bias thereof directly with variations of said error voltage, andfurther means connecting said amplified error voltage With saidpotential responsive control element to vary the impedance of said 10input circuit inversely with variations of said error voltage.

Vance Mar. 11, 1941 15 8 Livingston Oct. 29, Philpott Ian. 5, HallerOct. 12, Koch Aug. 23, [Crever et 211. Mar. 11, Hutcheson et a1. Apr. 6,Bixby' Jan. 7, Pooh Sept. 9, P gor-zelski June 1-3, Wellons June 5,Schultz July 31, Potter Dec. 4, Lupe Apr. 29, Kurshan Dec. 30,

